Presentations · Glossary
What is a thesis defence (viva)?
A thesis defence is the oral examination of a research degree, where the candidate discusses and justifies their thesis in front of examiners who have already read it. In the UK it is called a viva, in the US a dissertation defense, and in Australia it has traditionally been replaced by written examiner reports, though some universities now hold one.
The same words describe very different events depending on the country, from a private conversation with two examiners to a public talk with a committee and an audience. Knowing which kind you face decides whether you need a polished presentation, a handful of reference slides or none at all.
Indunil Asanka · Co-founder
5 min read · Published
| Australia | United Kingdom | United States | |
|---|---|---|---|
| Examiners | Usually two, external to the university | Usually two, one internal and one external | A committee of the candidate's faculty, with a chair |
| Oral examination | Traditionally none; some universities now hold one | A viva is the norm | A defense is the norm |
| Public or private | Where held, often private; some faculties add a public talk | Private, not recorded at Cambridge | Public presentation, then a closed session |
| Length | Varies where an oral is held | Normally 90 minutes to three hours at Cambridge | Presentation about 30 to 60 minutes at Boise State, then questions |
| Slides | Only for a public presentation, if required | Only if the candidate is told to present | Expected for the public presentation |
An examination of the thesis, spoken aloud
By the time a defence happens the thesis has been submitted and read. The examiners are not hearing the research for the first time; they are testing whether the candidate wrote it, understands its limits, can place it in the field and can answer challenges to the method and the claims. That is why the event feels more like a demanding conversation than a lecture. Outcomes range from a pass with no changes, through minor or major corrections, to resubmission. The defence rarely decides the result on its own, because examiners have usually formed a view from the written thesis, but it can move a borderline case in either direction and it settles which corrections are required.
Australia, the United Kingdom and the United States
Australia first. The PhD has traditionally been examined by written reports from two examiners outside the university, with no oral, and the University of Queensland still runs a path in which the examination consists of thesis evaluation alone. Practice is changing: the University of Sydney describes its oral examination as a private session with the candidate, the two examiners and a Chair of Examination, and notes that some faculties also require a public presentation beforehand. In the UK the viva is standard. Cambridge describes two examiners, typically one internal and one external, no set duration but normally 90 minutes to three hours, a session that is not public and cannot be recorded, and a presentation only when the candidate is told at least two weeks ahead. In the US a public defense is common: Boise State describes a research presentation of about 30 to 60 minutes open to the university community, followed by private examination and a closed committee discussion.
Preparing the presentation part
Where slides are needed, they should summarise rather than retell. Examiners have read every chapter, so the method gets one slide and each results chapter gets one slide with its central finding. A strong defence deck states the research question early and returns to it at the end, raises limitations before the examiners do, and makes the contribution explicit, ideally as a few claims each tied to the chapter that supports it. For a public defense, the audience includes people outside the field, so the opening needs a plain explanation of why the question matters. Keep backup slides with detailed tables after the final slide, ready for a question about a specific result, instead of cramming them into the main talk.
Common mistakes
The most common is presenting the whole thesis in order, which runs long and leaves little time for discussion. The second is defensiveness: treating every question as an attack instead of engaging with it, which examiners notice more than any single weak answer. The third is not rereading the thesis in the weeks before, so the candidate is surprised by their own chapter four. The fourth is skipping the limitations, inviting the examiners to find them. The fifth is preparing slides for a UK or Australian oral that never asked for them and trying to present anyway. The last is not checking the local rules, since length, audience and presentation requirements differ between universities and sometimes between faculties within one.
Defence decks in the slide builder
The thesis defence example linked on this page is a twelve slide deck for a 30 minute viva on how street tree canopy changes summer surface temperature across 14 suburbs: a formal typographic cover, a five part agenda, methods in four steps, one slide per results chapter, limitations before the contribution, future work and a questions slide that restates the sub questions. A similar deck can be generated from a brief and edited slide by slide. While presenting, speaker notes can pop out into a separate window on your own screen and a pen or highlighter can mark a figure during a question; those tools and recording need a paid plan. The example library also holds an A0 thesis defence poster for programmes that ask for one.
Questions people ask
Can you fail a thesis defence?
It is possible but uncommon, because supervisors and universities usually do not allow submission of a thesis that is not ready. The more common outcomes are minor or major corrections. Where a defence goes badly, examiners more often require resubmission or further work than an outright fail, and the rules of the specific university set out the options.
Who attends a UK viva?
Normally the candidate and the two examiners, and sometimes an independent chair who manages the process without examining. At Cambridge the supervisor cannot attend. Some universities let a supervisor sit in silently with the candidate's agreement, so check the local regulations and ask the graduate school if the guidance is unclear.
What questions do examiners usually ask?
Expect an opening question asking the candidate to summarise the thesis and its contribution, then questions on why a method was chosen over alternatives, how the findings relate to key literature, what the limitations mean for the conclusions, and what the candidate would do differently. Many finish by asking about publication plans and future research.
How should I prepare in the final weeks?
Reread the thesis with a notebook and mark weak points, typos and anything that has since been published nearby. Hold a mock defence with colleagues who ask hard questions, and practise answering briefly then stopping. Bring an annotated copy of the thesis to the room, since referring to your own pages is normal and expected.
Is a master's thesis defended the same way?
Often not. Many coursework and research master's degrees are examined on the written thesis alone, and where an oral exists it is usually shorter and less formal than a doctoral one. Rules vary widely between universities and countries, so the programme handbook is the only reliable guide.
Can a thesis defence be held online?
Many universities now allow it. Cambridge, for example, holds vivas in person by default but allows a remote or hybrid examination by video. For an online defence, test screen sharing and audio on the actual platform beforehand and have a PDF of the slides ready in case sharing a live presentation fails.
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